Apparatus for multi-diameter thread rolling



July 17, 1962 H. F. SEIBERT APPARATUS FOR MULTI-DIAMETER THREAD ROLLING Filed April 11. 1958 2 Sheets-Sheet 1 INVENTOR Howard E Seiber/ BY W ATTORNEY July 17, 1962 H. F. SEIBERT 3,044,329

APPARATUS FOR MULTI-DIAMETER THREAD ROLLING Filed April 11, 1958 F76. 6 /27\rT n A m 52 2 Sheets-Sheet 2 INVENTOR ATTORNEY United States Patent Office 3,044,329 APPARATUS FOR MULTI-DIAMETER THREAD ROLLING Howard F. Seibert, Lebanon, Pa., assignor to Bethlehem Steel Company, a corporation of Pennsylvania Filed Apr. 11, 1958, Ser. No. 727,946 6 Claims. (Cl. 80-9) This invention relates to an improved method and apparatus for rolling continuous male threads of more than one pitch diameter on the same workpiece.

In forming a standard thread of single pitch diameter on an ordinary bolt, stud or pin, the cylindrical blank is rolled between oppositely moving grooved straight dies which impress the desired threads. When it has been required to roll continuous threads with two or more pitch diameters on the same workpiece, the usual practice has been to roll each pitch diameter in a separate operation and utilize a different pair of dies for each pitch diameter. Although it is obviously desirable to be able to roll multi-diameter threads at one time and in one operation with a single pair of dies, the requirements of skill, difficulty and cost involved in cutting grooves of precisely the same form but very slightly and accurately differing depths on adjacent portions of one die face, and of duplicating such grooves on other dies, have been heretofore regarded as commercially insuperable. By means of my invention, however, I have been able to roll in one operation multi-diameter threads having very small differences in pitch diameter, e.g., on the order of .010" or .024 on a workpiece such as a stud or bolt of nominal /4 diameter, and to form the necessary dies virtually as quickly and economically as the dies for threaded articles of a single pitch diameter.

One object of this invention is to provide apparatus for rolling continuous male threads of more than one pitch diameter on a workpiece.

Another object is to provide a method of producing dies for rolling diametrically offset threads on a round workpiece.

An additional object is to provide thread rolling dies in which certain portions of their working faces are precisely adjustable inwardly or outwardly in relation to other portions of said Working faces.

Still other and further objects, purposes and advantages of the invention will appear hereinafter in the specification and claims, and also in the annexed two sheets of drawings, in which:

FIG. 1 is a plan view of a flat die with an insert for rolling two pitch diameter threads on a workpiece;

FIG. 2 is a side elevation, partly in section, of said die and insert while the thread rolling grooves are being cut;

FIG. 3 is an end view of said die showing the use of a shim behind the insert during the cutting of thread grooves;

FIG. '4 is a cross-sectional view of the operation of rolling a two pitch diameter thread on a workpiece;

FIG. 5 is an isometric view of the insert removed from the die;

FIG. 6 is a plan view showing the use of a die with two inserts and one shim for rolling three pitch diameter threads;

FIG. 7 is a side elevation partly in section of said three pitch diameter assembly during the step of cutting the thread forming grooves;

FIG. 8 is an end view of the three pitch diameter as sembly showing a shim disposed behind one of the two inserts during the grooving step;

FIG. 9 is a cross-sectional view of the operation of rolling three pitch diameter threads, with one shim in place and one removed; and

FIG. 10 is an isometric view of one of the inserts used in rolling three pitch diameter threads.

Referring to FIGS. 1 to 5 of the drawings, and more part cularly to FIG. 4, the typical workpiece shown has a hexagonal head 1 and a shank 2 upon which are to be rolled two groups of threads 3 and 4 of diiferent pitch diameters. The ungrooved blank of each of the counterpart dies 5 is longitudinally recessed on its inner face to form a slot 6 extending from approximately the longitudinal center of the die to the shoulder 7 at the work exit end of the die above the main die face 8. The width of this slot, as shown in FIG. 4, corresponds to the length of the larger threaded portion 4 of the workpiece. A shim 9,0f thickness equal to one-half the desired difference in pitch diameters, is placed within said slot 6. An insert 10 is then seated against the shim 9 in said slot 6 with the exposed face 11 of the insert flush with the die face 8, and secured by bolts 12 extending through insert holes 13 into threaded holes 14 in the die blank. The working faces of the assembled die blank 8 and insert 10 are then ground or milled together to form identical thread-rolling grooves 15 and 16 and work-gripping serrations 17 on the blank and insert. The shim 9 is then permanently removed, and the die and insert are conventionally hardened by heat treating or the like prior to thread rolling.

The above-described sequence of placing a shim 9 behind flush insert 10, cutting the grooves 15 and 16 on die and insert simultaneously, and reassembling and using the die and insert without the shim, will obviously cause that portion of the workpiece which is rolled between the inserts to have a larger pitch diameter than the portion rolled between the main die portions. Conversely, if the portion to be rolled between the inserts is to be made smaller, the working faces of the flush insert 10 and the main part of the die may be ground without shims, which can be inserted later but before the rolling operation.

These operations may be very conveniently combined for the purpose of rolling three pitch diameter threads, as shown in FIGS. 6-10 of the drawings. In this situation, the workpiece may have a conventional hexagonal head 18, alarge upper threaded portion 19, an intermediate sized middle threaded portion 20, and a small end threaded portion 21, on which the threads are formed by the working faces of the top insert 22, main die portion 23, and bottom insert 24 respectively. Before the inserts 22 and 24 and the main die portion 23 are ground, a shim 25 is placed behind the top die insert 22, but not behind the bottom die insert 24. After the dies and inserts have been ground, the shim 25 is removed, the dies and inserts are hardened, another shim 26 (or the first shim 25) is placed behind the bottom insert 24, and the assembly is fastened together by bolts 27 and 28.

Although I have thus described my invention hereinabove in considerable detail, I do not wish to be limited narrowly to the exact and specific particulars disclosed, but I may also use such substitutes, modifications or equivalents as are included within the scope and spirit of the invention or pointed out in the appended claims.

I claim:

1. A thread rolling device including a die having thread rolling grooves 'across the face thereof, said die having at least one longitudinal slot on said face, a die insert in said slot having on its face thread rolling grooves of the same pitch and form as the grooves on the die face and continuous with the grooves on the die face, and means for laterally offsetting the face of the die insert in substantially fixed relation to the die face.

2. A device for forming spiral screw threads on a cylindrical blank, comprising a pair of cooperating rolling dies, each die having a series of angular grooves for forming one thread portion on the blank, and a laterally adjustable insert which is fixedly attached to said die dur- Patented July 17., 1962* 7 continuous with the first such portion but of different pitch diameter therefrom.

3. A device for forming screw threads of more than one pitch diameter on a cylindrical blank, comprising a pair of parallel dies which are operationally arranged to be reciprocated solely endwise for-simultaneously acting upon opposite sides of the blank, at least one die insert in the working face of each die, said dies and die inserts having parallel thread forming grooves, and a spacing member insertable between each die and die insert for laterally displacing the insert to a firmly fixed operating position in relation to the die so as to eifect a radial ofiset between threaded portions formed on the blank by the Working faces of said die and die insert.

4. A device for rolling a plurality of groups of screw threads of difierent pitch diameters on a cylindrical blank, comprising a pair of parallel dies upon opposite sides of the blank having their faces grooved to form a first group of spiral threads on the blank, each die face having at least one longitudinal' slot, a shim in said slot of thickness equal to one-half the difference in pitch diameters between adjacent thread groups, and a die insert aflixed in said slot and spaced outwardly by said shim, said die insert being grooved on its outer face to form a second group of'spiral screw threads of equal pitch and shape but different pitch diameter relative to the first group.

. 4 e 5. A thread rolling device for simultaneously forming continuous spiral threads of like form and pitch but of different pitch diameters upon a cylindrical blank, comprising a pair of die sections having thread rolling grooves across their faces of the same form and pitch, said pair of die sections being tightly bolted to each other with their thread rolling grooves in continuous relationship and References Cited in the file of this patent UNITED STATES PATENTS 408,529 Rogers Aug. 6, 1889 470,805 Jones Mar. 15, 1892 1,521,322 Reed Dec. 30, 1924 1,525,536 Debrot Feb. 10, 1925 1,649,929 Senior Nov. 22, 1927 1,912,879 Arenz June 6, 1933 2,161,610 Boggild June 6, 1939 2,165,008 Rosenberg July 4, 1939 2,256,269 Stoll -1 "Sept. 16, 1941 

